This invention relates to thermoplastic polymers which are useful in molding centers for golf balls. More particularly, it relates to the use of thermoplastic polymers composed of block radial polymers of the dienearyl substituted olefin butadiene-styrene type which contains a major portion of a filler material to form a core wall for a liquid golf ball center offering versatility in meeting manufacturing specifications as well as high production rates with precise size and weight control.
Currently golf balls are produced in the following forms:
1. A one component solid construction composed of a homogeneous mass consisting of polybutadiene, monomers, fillers, antioxidants, curing agents, etc. PA0 2. A two component golf ball comprising a cover composed of natural rubber (Balata) or plastic (Surlyn) including urethane; and a core composed of a solid homogeneous mass similar to Item #1. PA0 3. A three component golf ball composed of a cover composed of Balata rubber, plastic (Surlyn) or similar material; a winding composed of natural and/or synthetic rubber thread; and a core made from natural or synthetic polymers. PA0 4. A four component golf ball having a cover as described in Items 2 and 3; a winding as described in Item 3; a core wall made from natural and/or synthetic rubber; and a liquid center composed of glycerin, polyethylene glycol, salt solutions, etc.
The golf ball center of the type concerned with in this invention is the Core Cover in Item 4. Golf balls with liquid filled centers are popular because the liquid cannot be compressed, but does deform upon impact from the golf club, thereby allowing the golfer a wide range of control. This is accomplished because, for a given compression, there is more ball in contact with the club head at the moment of impact. This segment of the four-component construction is costly to produce as it entails the encapsulation of an exact amount of liquid within a rubber covered sphere.
Block copolymers of butadiene-styrene and styrene-butadiene-styrene type are described in U.S. Pat. No. 3,534,965 to produce a solid golf ball. The block copolymers are blended and cured to result in the solid golf ball. Styrene-butadiene copolymers are also vulcanized in a blend with a polytetrahydrofuran to form a molded golf ball in U.S. Pat. No. 3,373,123. In U.S. Pat. Nos. 4,048,254 and 4,048,255 blends of uncured radial block copolymers are described for use with a third polymeric material for use in making thermoplastic materials for pharmaceutical purposes. The prior art nowhere describes a noncross-linked, butadiene-styrene radial block copolymer having a specific butadiene and styrene content in combination with a major portion of a filler material for use in the manufacture of a core wall for a liquid golf ball center. Neither does the prior art indicate that a noncross-linked butadiene-styrene radial block copolymer can be employed in formulations for composing liquid golf ball centers wherein the use of fillers and extenders can be freely incorporated to obtain centers meeting precise manufacturing specifications and at high production rates.
It is an advantage of the present invention to provide a core wall for a liquid golf ball center composed of a noncross-linked butadiene-styrene radial block copolymer. Other advantages are a liquid golf ball center containing a major portion of filler material as well as extenders so as to permit versatility in achieving desired properties for a golf ball; a liquid golf ball center which can be molded by various molding techniques including injection molding so as to afford rapid production as well as size and weight control; a liquid golf ball composition which eliminates the need for curing and permits the reuse of any trim and runner system material.